/Engine/Plugins/FX/Niagara/Source/NiagaraEditor/Public/NiagaraGraph.h
Changes the type of existing graph parameters. Optionally creates orphaned pins for any connection that won't be kept, but tries to keep connections as long as types are matching. Changing multiple parameters at once helps with maintaining connections. CAUTION: Do not allow orphaned pins in the stack graphs, as they aren't user facing.
void ChangeParameterType ( const [TArray](API\Runtime\Core\Containers\TArray)< [FNiagaraVariable](API\Plugins\Niagara\FNiagaraVariable) > & ParametersToChange, const [FNiagaraTypeDefinition](API\Plugins\Niagara\FNiagaraTypeDefinition) & NewType, bool bAllowOrphanedPins )